Field of the Invention
The present invention relates to a physiologic detection device, particularly to a multi-focus physiologic sensing device for efficiently condensing light.
Description of the Related Art
With technological advancements, in recent years the development of wearable physiologic detection devices is more and more popular, such as physiologic sensing watches. An optical detection method is generally used in the traditional technology. A lighting element is used to generate a light source which is incident on a detected skin, and then the method senses the optical signals reflected by the skin. The method analyzes the intensity variation of the light with different wavelengths after penetrating physiologic tissue, and uses the variation to figure out physiologic values such as heart rates, blood oxygen, and blood sugar. However, if the intensity of the light source is insufficient, the light source is easily affected by noise of environment light without penetrating the skin and the physiologic tissue. As a result, the physiologic values will not be precisely measured.
In order to increase the condensing efficiency of light, a condenser is added to increase the intensity of light, thereby increasing a signal to noise (S/N) ratio. The condenser used in the prior techniques has a small light-collection angle, such as a Fresnel lens, whereby the condensing efficiency is not improved efficiently. Besides, when heart rates, blood oxygen, and blood sugar are measured, the light sources with different wavelengths are used. If the condenser with one focus is merely used, the light sources with different wavelengths cannot simultaneously be analyzed, which leads to measuring an imprecise physiologic state.
Take a U.S. Pat. No. 5,995,856 for example. Refer to FIG. 1, which shows an upper casing 90 and a lower casing 92 under the upper casing 90. The upper casing 90 has an upper concave mirror 902 and a physiologic sensor 904. The lower casing 92 has a lower concave 922 and a lighting element 924. The lighting element 924 projects light on the lower concave 922. The lower concave 922 condenses and reflects the light to a detected skin 94. Then, the detected skin 94 reflects the light to the upper concave mirror 902 to project the light on the physiologic sensor 904 for physiologic state detection. However, the US patent does not mention that the condensing efficiency is increased by adjusting curvature of a reflection surface of the concave mirror. In addition, measuring various physiologic signals requires processing and sensing the light sources with at least 2˜3 different wavelengths. Nevertheless, the US patent cannot detect different physiologic signals by simultaneously using the light sources with different wavelengths. Accordingly, the US patent cannot measure physiologic signals such as heart rates, blood oxygen, and blood sugar.
To overcome the abovementioned problems, the present invention provides a multi-focus physiologic sensing device for condensing light, so as to solve the afore-mentioned problems of the prior art.